Based on what? Can you be SURE that a new tank will be 'perfect'?
His 8'x2'x2' has ~48' of seams... Does 1 small problem mean that "the tank was obviously not built right from the get go"
Well in 20+ years of professional fabrication I can tell you that a properly welded joint is stronger than the panel itself. The panel is the weak part and not the joint in a acrylic tank.
So yes I can be SURE without a doubt that a tank that's been designed and built correctly from the start would not be having these issues.
So seeing as this tank has had one weld fail the probability of it continuing is extremely high.
I can't tell for certain, but from the pictures it looks like the tank was built by Tricon, an old company out of Seattle that's no longer in business. Skippy built some decent quality tanks but they definitely were't Envision quality and quite a few of them developed issues overtime.
If I were to build that tank I'd use 1" for the build with the exception of the bottom panel. You could go 3/4 on the sides but I'd prefer to use 1". 1/2" for the bottom of the tank is fine.
Another concern is the radius on the cutouts of the eurobrace, they are too small and can be prone to failure even with the small cutout size.